Reverts third_party/protobuf: Update to HEAD (f52e188fe4)

third_party/protobuf/csharp/src/AddressBook/SampleUsage.cs

Index: third_party/protobuf/csharp/src/AddressBook/SampleUsage.cs
diff --git a/third_party/protobuf/csharp/src/AddressBook/SampleUsage.cs b/third_party/protobuf/csharp/src/AddressBook/SampleUsage.cs
index b4ab8d8f36f964f41cd46b34952cee17804c7afe..aad7d700278a80712d43b7436f52ecd80b1f1cc7 100644
--- a/third_party/protobuf/csharp/src/AddressBook/SampleUsage.cs
+++ b/third_party/protobuf/csharp/src/AddressBook/SampleUsage.cs
@@ -66,7 +66,7 @@ namespace Google.Protobuf.Examples.AddressBook
             // The message performs a deep-comparison on equality:
             if (restored.People.Count != 1 || !person.Equals(restored.People[0]))
             {
-                throw new Exception("There is a bad person in here!");
+                throw new ApplicationException("There is a bad person in here!");
             }
         }
     }